1. Field of the Invention
The present invention relates to an air cleaner for cleaning air by removing visible or invisible foreign materials, for example, fine particles such as dust and cigarette smoke and various types of gases that produce bad odors, and airborne infectious microorganisms such as bacilli, molds and bacteria.
2. Related Arts
The air in various areas, including living and working spaces, differently sized assembly spaces and a variety of recreation locations such as pachinko parlors, and the compartments of transportation means such as vehicles, airplanes and ships, contains undesirable visible and invisible foreign materials, such as fine dust particles and cigarette smoke, various types of air pollutants, airborne infectious microorganisms and volatile organic gases generated by chemical materials, including adhesives and paints, and gases generated by human beings and a variety of manufactured products.
Most of these undesirable, fine particles and gases are harmful to human beings, and the content of these foreign materials in the air must be maintained at an extremely low level when processing is performed for super precision manufacturing devices and apparatuses, such as semiconductor devices, and the manufacture and processing of medical and pharmaceutical products, and in specific rooms in medical institutions. To satisfy this need, a so-called clean room is required, and for this, various air cleaning systems have been developed.
As a dry dust removal system, a downflow system is widely employed for clean rooms employed for the manufacture of semiconductor devices and integrated circuits. According to this system, air is passed through an extremely fine filter to adjust and to optimize temperature and humidity states. The air is then introduced into a room from the ceiling, and is discharged downward through a mesh floor. However, this dry dust removal system is effective only for the removal of solid dust, such as fine particles, but is less effective for gases. Further, the filter is easily clogged, and the initial characteristics can be maintained only for a short period of time. Also, when a finer filter is used, the frequency to perform the maintenance for the apparatus is increased.
On the other hand, another popular technique is one whereby, to clean the air, visible or invisible foreign materials, such as dust and gases, are removed by using water or another liquid. According to this technique, undesirable, fine particles and gases are removed from the air while the air is passed through water, or through a layer of fine water droplets that is formed by a water spray. This is a wet dust removal system technique that cleans the air by employing fine water droplets to dissolve fine particles and gases, through air-liquid contact, and uses the fine water droplets to remove the foreign materials.
It is known that not only is the air cleaning process performed during the air-liquid contact process, but that also during this cleaning process air bubbles are exploded and fine water droplets are separated to produce a large quantity of negative ions. As is well known, especially near forests and waterfalls there are many negative ions and they effectively act on human bodies, e.g., they are effective for recovering from fatigue and for physical and mental stabilization. Therefore, the air-liquid contact system that uses fine water droplets has drawn people's attention as an appropriate air cleaner for living spaces, working spaces such as offices and areas where many people assemble.
As a compact air cleaner developed for home use or office use, an air cleaner is disclosed in Japanese Patent Laid-Open Publication No. Hei 4-126717, for example, that comprises: a spray tower through which air to be cleaned is passed, while a pump is employed to spray pressurized water through nozzles; and a cyclone tower for rotating air after it has passed through the spray tower and discharging it to the outside. With this configuration, air introduced into the spray tower by a fan is cleaned, and following that, air obtained by air-liquid separation is discharged.
According to this air cleaner, when sprayed water and passing air contact each other in the spray tower, fine particles and contained gases are dissolved in the water, and thereafter, since water droplets collide with the wall face and are separated, finer water droplets are formed. Then, while an air stream formed of very fine water droplets is rotated within the cyclone tower, centrifugal force exerted on the air causes an air-liquid separation and clean air is discharged to the outside. However, with this arrangement, since the water spray resembles a shower ejected from an upright spray cylinder provided in the center of the spray tower, the efficiency with which the contact obtained between the water droplets and the air to be cleaned is less, and a satisfactory cleaning process can not be performed.
To resolve this shortcoming, disclosed in Japanese Patent Laid-Open Publication No. 2000-42338, for example, is another device wherein, in front of multiple spray nozzles, multiple, slightly displaced partitions (blocking plates) are formed and wherein a thick water screen layer is formed by the collision of sprayed water with these partitions, so that air to be cleaned passes through the water screen. Since, the air passes through the thus formed water screen after large dust particles have been removed from the air by a prefilter, a better air-liquid contact is obtained, thereby increasing the effects provided by the catching of fine particles and gases. However, since the partitions with which the sprayed water stream collides provide an air channel having only a narrow effective area, airflow resistance is increased, and accordingly, a fan having a larger capacity is required.
The use of a fan having a large capacity is not only contrary to the desired, energy saving objective, but is also contrary to the formation of a friendly environment because the fan generated noise is increased. While taking these facts into account, disclosed in Japanese Patent Laid-Open Publication No. 2002-119819, for example, is another device wherein multiple, opposing spray nozzles are provided in an air-liquid contact space and sprayed water particles collide with each other, forming a satisfactorily thick water screen without requiring the partitions (blocking plates) that can produce an increase in the airflow resistance.
According to this device, since two air-liquid spaces are arranged by using the opposing spray nozzles that are provided, a more effective air-liquid contact is ensured, and the capture of fine particles and gasses is more complete.
According to the above described configurations that use air-liquid contact, circulating water in a water tank is repeatedly employed for cleaning the air, and depending on the usage environment, the water becomes contaminated within a short period of time and produces a bad odor, so that the early cleaning of the water tank and the exchange of the water it contains are required. Furthermore, these conventional air cleaners do not provide the sterilization and deodorization processing required for the infectious microorganisms that are suspended in the air.